(1) Field of the Invention
The present invention relates to a medical solution transfusion circuit having a cylindrical pumping body such as a drip chamber in a solution administration or blood administration set and, more particularly, to a medical solution transfusion circuit which can be easily assembled by ultrasonic welding and which has a cylindrical body suitable for radiation sterilization and having good pumping characteristics and high transparency.
(2) Description of the Prior Art
Conventional circuits are used to transfuse medical solutions such as an infusion solution and blood in medical treatments (e.g., solution administration or blood administration) and extracorporeal blood circulation treatments (e.g., dialysis and artifical heart and lung treatment). These medical solution transfusion circuits each comprise a cylindrical body such as a drip chamber having a drip port for dripping a medical solution in the drip chamber, and a flexible tube connected to the drip chamber to transport the medical solution. In this case, the drip chamber is transparent to allow checking of a drip rate of the medical solution.
Flexible tubes for transfusing a medical solution are connected to two ends of the cylindrical body which is made of flexible or semi-rigid vinyl chloride resin and incorporated in the medical solution transfusion circuit. When the medical solution transfusion circuit is assembled, the two ends of the cylindrical body are adhered by an organic solvent such as cyclohexanone and tetrahydrofuran to the separately formed components such as drip port members and the flexible tubes. Alternatively, the two ends of the cylindrical body are adhered by an organic solvent to a hard cap having the drip port formed therein.
However, when an organic solvent is used as an adhesive, the solvent permeates into the inner space or inside the material at the adhered portion and its vicinity and is left there. The solvent left inside the material weakens the mechanical strength of the material. In addition to this disadvantage, the solvent left in the inner space may be eluted in the medical solution when the cylindrical body is used. These disadvantages cause grave problems in the medical solution transfusion circuit.
In addition, the flexible vinyl chloride resin has a low elasticity and cannot restore its original shape when pumping occurs. However, even when the amount of a plasticizer is decreased to improve the restoration force, crazing occurs if the cylindrical body pumps several times. Furthermore, when the flexible vinyl chloride resin is sterilized with gamma-rays, the resin is discolored, and an amount of extract increases. In addition to these disadvantages, a pH value greatly changes, and consumption of potassium permanganate is increased.
A flexible transparent material subjected to pumping comprises an ethylene-vinyl acetate copolymer, an ethylene-ethylacrylate copolymer, a styrene-butadiene based copolymer, or a denaturated copolymer of poly(4-methylpentene-1). When the denaturated copolymer is formed into a thin cylindrical body, it may be crushed and cracked by pumping, and microorganisms may be introduced into the medical solution. This denaturated copolymer is thus not suitable as a material for a drip chamber. The styrene-butadiene copolymer is not practically used since a drip chamber thereof is easily crushed by pumping and will not restore its initial cylindrical shape. The ethylene-ethylacrylate copolymer is toxic due to the presence of ethylacrylate. The ethylene-vinyl acetate copolymer is not sufficiently transparent. The above copolymers absorb ultrasonic vibrations due to their flexibility when they are welded by an ultrasonic welder and thus are not suitable for ultrasonic welding.